Method of cutting straight, helicoidal, and conical gear-teeth.



L. oIsARD. METHOD 0I' CUTTING STRAIGHT, EELIGOIDAL, AND UONIOAL GEAR TEETB.

APPLICATION FILED JUNE 1,1905. 906, 1 89. Patented Dec. s, 1908.

2 SHEETS-SHEET 1.

- FIG-4.-

L. BoIsABD. METHOD 0F CUTTING STRAIGHT, HELIOOIDAL, AND OONIOAL GEAR TEETH.

APPLIOATION FILED Jmrz'l, 1905. 1

Patented Dec.8,1908.

2 SHEETS-SHEET 2.

zpi 700W UNITED STATEsPATENT vonirica.

LOUIS BOISRD,.F.LYON FRANCE. :METHODv OF CUTTIG STRAIGHT,"HELICQIDA L,:AND CONIQL GEAR-TEETH.

Specification of Izetter's Patent.

Patented D'ec; 8', 1908.

Appu'caeon mea :une 1, 1905. serial No. 263,225.

Y tween the two extreme pitches for which the cutter has been designed.

Since the cutter when used in the manner hereinafter described is capable of cutting teeth of profile suitable for'true rolling contact at an pitch between the two said extreme pitc es, it can be used not only for the teeth of cylindrical wheels; but falso for i near the apex .-andi.. the

teeth of beveled Wheels providedthepitch pitch furthest from the apex do notrespectively sur ass thefsaid extreme pitches. l' ltcan` also" e used for cutting helicoidal teeth on cylindrical and beveled gear wheels.

The cutter is produced by the super osition of two threads and is the subject o another patent granted to me 1st October 1907 The invention .is illustrated'in the annexed drawing, in which- Figure 1 is a view, illustrating the cutting of the teeth of a beveledwheehthe. cutter being 4in the position corresponding. to the cutting of the .teeth where .thexpitch :is smallest namely near the? apex of- .the

cone. Fig. 2 -is asimilar view ,illustrating the position of the cutter when the largest itch is being cut. Fig; 3 is a sectional view illustrating the action of the cutter on a beveled wheel blank. Fig. 4 is a pers ective view of the cutter. Fig. 5 is a viewi ustrating the cutting of the teeth of a straight wheel. Fig. 6 is a plan view of the same, and Fig. 7 is a sectional view illustrating the action of the cutter on the blank.

a: indicates the cutter, y a beveled wheel, e a straight or cylindrical wheel.

In order that this invention may be more easily understood- I will first refer to the principles of the known-method of cutting :teeth by means *of helicoidal cutters.

- with regard tothe pitc Straight and helicoidal gear teeth have` been cut hitherto b meansof milling cuttersrin l 'the form of he ices'the litch (22,) of whichis,

. exact.

previously referred to.

threadaofa given pitch Aon4 which .1s Asuperi be cut, in the ratio :-p= the angle contained by a me perpendicular to a generator of the primary cylinder of the helical cutter and by a tangent to the helix at the intersection of this generator.

The operation of cutting a wheel of 'n teeth is performed by inclining the cutter at the angle'a with regard to the plane of the wheel and by revolving said cutter and wheel in such a manner that the wheel makes one revolution while the cutter makes n revolutions.

Theihelical cutter as formerly used has a I suilicient number of convolutions so that'a longitudinal section approximates to a rack adapted to cut teeth which are theoretically lf the rack, that is to say the cutter, has teeth with straight symmetrical s ides, it cuts a Wheel the Pteeth of which are in prole cycloidaL-and consequently a' cutter with Wheel-With pitc p, for any number 10i teeth provlded, otcourse, that the "cutter has either asulicient number of convolutions to cosa where a is' continue cutting action on the teeth un til they are carried by the revolution of the blank out of the range of action of the cutting teeth or that a globular helical cutter is used.

The helical cutters hitherto used have had asingle thread of given pitch and a plurality of convolutions. My improved cutteip. is constructed 4in a dierent way which may be described herefor the better understanding of this: invention although the said cut-ter formsithe--subject'of a1. se -arate patentas t conslsts of a posed a thread of another pitch so that the cutting part is comprised only in that art which is common to the twoI threads. he constitution of this cutter is based on the theory that if the one thread is of pitch p1 adapted to cut a straight gear of pitc p, and. p p1 cosa and the other thread is of pitch 19% adapted to cut a strai ht ear of pitch p, the cutter will be suita le or cutting either of the itches p or vp and also any pitch-interme iate between p and p". To cut acylindrical Wheel with this cutter, for `example a Wheel with 'n teeth `of pitch p, it will be necessary to giveto the wheel an angleiof 4inclination a' corresponding to;. the -pitch p.

Aconvoutions Ais insufficient-.fte allow vof; ap-

.. alternately displaced, the blank be' can be obtained, the cutter be' proximatin the cutter to a rack. It therefore, b necessary to compensate for the absence of a sutticie'nt number of convolutions of the thread by giving a supplementary movement by which the cutter while revolving about itsaxis, is longitudinally and moved about its axis to correspond with this inovement of the cutter so as to resent the hollows between `the teeth to t e cutting teeth of the cutter thread. The series of cutting teeth then successively assume a series of positions e uivalent to the extension of the cutting teet around a plurality of convolutions, thus producing a profile of true rolling contact and a theoreticall vv,accurate gear of pitch p will be`obtaine In an analoV ous manner a'wheel having u teeth of pito p inc ined at the angle p. ForC cutting a W eel with fn, teeth o a pitch pk between p and p the cutter is inclined at the angle ak corresponding to this pitch.

. the exact The gear produced when the cutter is placed at a fixed angle of inclination only has rofle at the `Eplnt where the pitch correspon to this inc ation. In cutting beveled gear the exact prole at all oints is obtained b progressivel varying t e inclination of t e cutter-holder between the angles correspondin :to the sinallest pitch and ments are imparted to the cutter.

, cutter'along its axis, du

to the largest pitc respectively.

During the cutting the following move- 1. Ositive rota movement related to that o .the gear whee to be cut represented by arrows 1,

2 respectively in Figs. 1, 2 and 3 and 1 a and 2 in Figs. 5 and 6, the gear wheel making one revolution while the cutter makes n revolu-` tions (n being the numberl of teeth on the gear). 2. An alternating movement of the :which it moves with' it the wheel to be cut, in order to comensate for the insufficient number of convoutions of thread on .the cutter, as shown by in Fig. 6. 3. l-A forward movement of the cutter tan entially to the base of the toothspaces an following 'the generator of the cone or cylinder through the point of contact as indicated by arrow 3 inFigs. 2 and 3 or 3a in Figs. 6 and 7-. For .cutting beveled 4ears a fourth movement is necessary namey a movement which changes in a continuous manner, the inclination of the axis between the angles correspondin pitches of the gear as will e'seen by compar- 111g the an le of inclination of the cutter in 60"? I he s stem described can ting hehcoidalbevel-gears as' well as for cut' ft' F' s 1 an 2 respectively.

4istzraight gears. For this purpose it is cient to incline the cutter, with re ard Ato ofthe gear, at an' angle equ to the lposed threads of different to the extreme -inclinationwof the helicoidal teeth, without prejudice to the variable inclination'co'rre# 'sponding' t the pitch. The cutter advances the base `off-the tooth-A tangentially alon cgllng to the tangent ofthe spaces, but accor Ahelix wound bn the cone, which determines theggear, as isdone in the Godinot machine for cutting helicoidal cylindrical gears. For

the same purpose a differential'device might gears with a cutter the cutting teeth of which parts common to two are comprised' in the superposed threads of different pitches, said method consisting in placing vthe cutter with its axis inclined at an 'angle corresponding with the Ipitch of the teeth to be cut, and giving tot eA cutter and blank the follo relative movements, namely, a movement o translation of the cutter along therl generator of the blank, a reci rocato movement of the cutter tangentia to the lank, and relative rotational movement of the blank and cutter each on its axis,

2. The method for cutting beveled gears with a cutter the cutting teeth of'which are comprised inthe parts common to two supermethod consisting in giving to e cutter and blank the following relative movements, namely, a movement of translation of 'the cutter. along thegenerator of the blank a -movement of progressive inclination of the axis of the cutter to a plane containing the axis of the blank in proportion to the 1nlcrease of pitch, a reciprocatorjP movement of f the cutter tan ential to the b ank, and relative rotationa movement of the blank and cutter each on/ its axis.

3. Themethod for cutting beveled ears withv a cutter the cutting teeth of whic are comprised'in the parts common to two superposed threads of different pitches, said method consisting in placing the cutter with its axisinclined at an angle corresponding with the itch of the teeth to be cut at the smallest ameter of the blank, and giving to the cutter and blank the following relative movements, namely a movement .of'trans lation of the cutter along the generator of the blank, a movementof progressive increase of inclination vof the axis of the cutter to a plane containing the axis ofthe blank as the cutter descends the generator, a reciprocatory movement; of the cutter tangential to the blank, and relative rotational movement v of the blank and cutter each on^its axis. be used for cutg 4. The method for cutting helicoidal gears v'with a cutter the cutting teeth of which are comprised 1n the parts common .to two superposed threads 'of different pitches, -said method consisting'in placing thev cutter with itches said di occiso helical an le ofahe ear andr ivin to thes g s cutter and b e following relative movements, namely, a movement of translation of the cutter ,along the generator of. the blank, a reciprocatory movement ofthe cutter tangential to the blank, and relative rotational movement of the blank and cutter each-on its axis.

5. The method for cutting helicoidal beveled gears with a cutter the 'cutting teeth of which are com rised in the arts common to two superpose threads of erent pitches, said method consisting in placing the cutter with its axis inclined at an angle equal to the algebraical sum of the sponds with the pitch of the teeth. to be cut le which corresponds angle which correat the smallest diameter of the blank, andthe helical angle of the gear, and giving to thcr cutter and blank the following relative movements,gnamely, a movement of translation of the cutter along the generator of the blank, a movement of progressive increase of inclination of the axis of the cutter to a plane cgntaining the axis of the' blank as the cutter descends the generator, a reciprocatory movement vof the cutter tangential to the blank, and relative rotational movement of the blank and cutter each on its axis.

In witness whereof I have signed this specification in the presence of two witnesses.

LOUIS BOISARD.

' JmNAGnnmIN,

GUILLAUME PIQCHE. 

